Harvest is the process of gathering mature crops from the fields. The goal of good harvesting is to maximize crop yield and minimize any crop losses and quality deterioration. Harvesting can be done manually, using hands or knifes and it can be done mechanically with the use of rippers, combine harvesters or other machines. Regardless of the method farmers use, several guidelines should be followed to ensure that harvest losses are minimum and crop quality is perserved during harvest operations, such as harvest time, method, duration, and postharvest processes. There are different methods farmers can use to determine the right time for harvesting: moisture content of grains, sugar and nutrient content of fruits, visual properties of mature fruits (color, scent, size), counting of the vegetation season days caracteristic for each variety, etc.
Principles of Harvesting
There are a few principles followed by farmers while harvesting:
- Slicing with a Sharp Smooth Edge
- Tearing with a Rough Serrated Edge
- Single Element with High-Velocity Impact and Sharp or Dull Edges
- Two Element Scissor Type or Shearing Type cutting
Evapotranspiration = Evaporation + Transpiration
Evapotranspiration is considered as one of the most important components of the hydrological cycle. On the Earth’s surface, evapotranspiration plays an important role in context of water-energy balance and irrigation, as well as agriculture practices. Efficient use of water resources in semiarid and arid agroecosystems of the World has become increasingly important because of rapid depletion of water resources, industrial development and population increase, drought conditions, and degradation of ground and surface water quality in many regions. As mentioned, evapotranspiration (ET), which is the sum of transpiration through plant canopy and evaporation from soil, plant, and open water surface, is the largest component of the hydrologic cycle. Furthermore, evapotranspiration includes water evaporation into the atmosphere from the soil surface, evaporation from the capillary fringe of the groundwater table, and evaporation from water bodies on land. Evapotranspiration also includes transpiration, which is the water movement from the soil to the atmosphere via plants. Transpiration occurs when plants take up liquid water from the soil and release water vapor into the air from their leaves.
Transpiration is the evaporation of water from plants. Most of the water absorbed by the roots of a plant—as much as 99.5 percent—is not used for growth or metabolism. it is excess water, and it leaves the plant through transpiration. Transpiration is very important for maintaining moisture conditions in the environment. As much as 10 percent of the moisture in the Earth’s atmosphere is from transpiration of water by plants. Also, transpiration occurs through the stomatal apertures,and can be thought of as a necessary “cost” associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients and water from roots to shoots.
Factors That Affect Transpiration
There are many factors that affect transpiration. One such factor is temperature. When temperatures increase, the stomata of leaves open and more water transpires. Plants that grow in warmer climates transpire more. Moisture levels of the air and soil are other important factors. When relative humidity of the air increases, there is more moisture in the air, so transpiration decreases. However, if there is more moisture in the soil, plants will transpire more because they are taking in more water. More wind also increases the rate of transpiration because it decreases the relative humidity around a plant. Of course, some plants also just transpire more than others. Plants that live in dry environments, such as cacti, have evolved to conserve water in part by transpiring less water. This allows them to thrive in arid regions like the desert. Also, the size of the leaf because a leaf with a bigger surface area will transpire faster than a leaf with a smaller surface area.
Evaporation happens when a liquid is heated. This means that the liquid’s molecules have to gain kinetic energy. As a liquid’s molecules gain kinetic energy, the molecules begin to spread apart and vibrate faster. This causes the liquid to change its state of matter from liquid to gas. Water is a common substance where evaporation will take place. When energy or heat is added to water, the bonds that hold the molecule together begin to break, causing it to turn from a liquid into a gas. The temperature at which water will turn from a liquid to a gas is its boiling point: 212 degrees Fahrenheit or 100 degrees Celsius. It is also one of the three main steps in the global water cycle. Evaporation happens on a global scale. Also, accounts for 90 percent of the moisture in the Earth’s atmosphere, other 10 percent is due to plant transpiration. In the water cycle, evaporation occurs when sunlight warms the surface of the water. The heat from the sun makes the water molecules move faster and faster, until they move so fast they escape as a gas. Once evaporated, a molecule of water vapor spends about ten days in the air. As water vapor rises higher in the atmosphere, it begins to cool back down. When it is cool enough, the water vapor condenses and returns to liquid water. These water droplets eventually gather to form clouds and precipitation.